pancreas cancer : Vaccine Improves Survival

An experimental vaccine for pancreatic cancer has produced promising results in an early trial, researchers report.

The survival rate for 60 patients getting the vaccine in addition to surgery and chemotherapy was 88 percent after one year and 76 percent after two years, doctors at the Johns Hopkins Kimmel Cancer Center reported Tuesday at a cancer meeting in Philadelphia. That is a marked improvement over the traditional 63 percent one-year survival rate and 42 percent two-year survival rate.

But it is a relatively small study that requires intensive follow-up before the findings can enter medical practice, Dr. Daniel Laheru, an assistant professor at the center, told a joint meeting of the American Association for Cancer Research, the National Cancer Institute and the European Organization for Research and Treatment of Cancer.

"There are clearly important challenges one has to overcome in designing a cancer vaccine," Laheru said. The major challenge is to get the body's immune system to recognize and attack the special proteins that distinguish cancer from normal cells.

"In disease, the key proteins are known," he said. "We don't know them for pancreatic cancer. Also, many cancer cells can secrete substances that allow them to evade the immune mechanism."

The Hopkins vaccine, developed by Dr. Elizabeth Jaffe, uses irradiated cancer cells, grown in a laboratory, that cannot multiply but secrete a substance, GM-CSF, which attracts immune cells.

A first vaccine shot is given eight to 10 weeks after surgery, with four booster shots in addition to chemotherapy and radiation.

The new trial follows an earlier study of 14 patients. Three of them are alive seven years later, an impressive result considering that all were at high risk, Laheru said. Blood studies showed that the immune systems of those three patients recognized specific cancer cells, he said.

While the Hopkins researchers continue to follow survivors of the 60-patient trial, plans are being made for a larger study, which will include 500 to 600 patients, Laheru said. At best, the vaccine would not be available for clinical use until much later in the decade, he said.

A successful vaccine would be a great help, said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. The current prospect for most pancreatic cancer patients is not good, in part because the disease is usually not detected early, he said. There are 32,000 new cases of pancreatic cancer in the United States each year, and about the same number of deaths, Lichtenfeld said.

"When compared to the historical data, these patients are doing better with this vaccine, and that is exciting," he said. "But while we have exciting results, there is a lot of work yet to be done."

One cautionary note is that the Kimmel Center is unusually good at treating pancreatic cancer, so it's not known whether other centers would get the same results, Lichtenfeld said.

Still, the Hopkins report is another sign that cancer vaccines, a hope for three decades, might now be working out, he said, citing recent successful reports on vaccines for melanoma and prostate cancer.

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